Fracturing/pressure pumping

Unconventional Development Approaches Health Check, and Where We Have To Go

The newly formed SPE Hydraulic Fracturing Technical Section is working on a project to identify a set of best practices for completions engineers. Once completed, they will be accessible to the entire SPE technical community.

Hand palm up with sand

The direction of unconventional developments has been a roller-coaster ride, not only in the realms of financing and profitability, but very much in the technical execution of the well construction and the completion phases, too. This is particularly the case for those aspects relating to the completion and hydraulic fracturing operations.

There are few parties, I believe, that would disagree that the drilling community rapidly delivered an extremely coherent and efficient learning curve, something that the completion/fracturing discipline has unfortunately been much slower to achieve.

This is not in the least surprising. Effectively extending conventional technologies and focusing on key requirements (i.e., getting from point A to point B) worked well for drilling teams. In a commendable and efficient manner, they were able to readily deploy and incrementally learn in an almost linear fashion. This achieved remarkable delivery records across all unconventional plays.

Completions however, namely hydraulic fracturing, has been a very different journey and involves solving a very different problem, one with many more variables, inherent complexities, and multiple degrees of freedom.

With each unconventional play potentially being distinct (just as with drilling), these differences can, however, extend to impactful areal trends and features within the plays, as well as subtle variations along individual lateral wellbores. For example, unlike drilling, the form (and even sequence) of an offset wellbore completion can easily affect the completion operations in the current wellbore.

It is quite likely that much of the initial misdirection of energy and effort resulted from an overenthusiastic application of conventional planar fracturing technology and knowledge to the unconventional environment. Perhaps the initial lack of effective diagnostic tools and approaches played a role, something that appears to have been understandably addressed in recent years. However, there was also a likely inherent engineering bias in the industry’s fracturing staff engineers.

The bulk of the industry engineers had entered unconventionals off at least 2 decades of well understood, well defined, and highly effective physics-based analysis of conventional planar fracturing operations.

Indeed, in some areas this fallacy continues. For example, proppant selection is ostensibly performed based on long-established criterion set in place in the 1970s and 1980s, and wholly appropriate to planar fracturing. Whereas the reality is that proppant plays multiple very different roles in unconventionals, bridging, plugging, wedging, diverting, etc.

This has led to a “tearing up of the rule book” situation within the sector (that is ongoing) as poorer-quality sands and micro-/nano-proppants find applicability, as well as quality ceramics for a strategic place in the fracture. Yet, you may ask any frac engineer to select proppant for unconventionals and they will almost immediately request data on performance at 2 lb/ft2, as though we are flowing through proppant packs across the entire created geometry.

This significantly enhanced level of complexity has led to a general failure of the linear model in terms of effectiveness in progressing optimum completion solutions. As a result, the early years of unconventional completion learning were largely “lost” in this linear way.

Lost to widespread “suck-it-and-see” methodologies and applying planar fracturing understanding, all combined with a “watch thy neighbor” approach and adopting changes incrementally. Nevertheless, ever adaptable, the hydraulic fracturing community continually acknowledged this failure and adjusted the strategy to suit when and where it could.

While some linear solution approaches continued, the initial steps of big data approaches then began to appear—intuitive (almost naïve even), simplistic, academically focused, and not very effective at all, but they offer an early glimpse of light at the end of the tunnel. Additionally, the ever-inventive drive for meaningful industry completion diagnostics, such as distributed temperature sensing (DTS), distributed acoustic sensing (DAS), along with downhole video, and now sealed wellbore pressure monitoring. We also have new test site data coming in, such as at the Hydraulic Fracturing Test Site 2 (HFTS2) in the Delaware Basin portion of the Permian Basin All of these developments likely mean that we are moving into a new era.

This shift in bias/influence from physics-based application/learning (using existing conventional fracturing knowledge) to data-driven emerging understanding is playing a fundamental role in this journey. It is also being more widely reported on and discussed.

Data are finally being used to make decisions and provide support to confirm/adjust the physics-based thinking; rather than data being selectively filtered that fits the preconceived bias. The outcome is that a range of new approaches are now beginning to impact fracturing deployment in real time and allowing for coherent “on the fly” frac design adjustment. In the past couple of years, this has meant that there is an emerging line of sight, in early-stage execution of real-time optimization and completion excellence and efficiency (as well as a better understanding of the physics, Fig. 1).

A comparison chart of data-driven and physics models.
Fig. 1—A comparison chart of data-driven and physics models. Source: Hector Klie, May 2021. https://jpt.spe.org/a-tale-of-two-approaches-physics-based-vs-data-driven-models

In understanding the difference that has taken place between the drilling and completions journeys, it is not at all surprising that the drilling community was the first to create a relatively coherent road map that exists in the published literature. One result is the consistent delivery of optimal practices and a healthy number of rapidly developed technology solutions.

In contrast, in the very extensive (several orders of magnitude more volumetric) hydraulic fracturing literature, we have multiple blind alleys, broken promises, treatises of underachievement, and convincing dead ends that are all littered and intertwined among the equally successful routes and advances.

This extensive miscellany and quality of the literature, while extremely pertinent at the time, can now be just as equally frustrating and almost impossible to work through to obtain clarity and insight that is applicable to the present day.

However, a solution is potentially at hand as the newly formed SPE Hydraulic Fracturing Technical Section (HyFTS) is proposing to provide a number of best practice whitepapers that declutter the hydraulic fracturing road map. An early idea is to focus the effort on the key advancements and insights that have been hard-achieved in the past 2 or 3 years—and most importantly, with an emphasis on the past 2 or 3 decades. The intent is to provide some clear direction for those wishing to move to the front quickly and be close followers of best practice.

There are a myriad of ways that this might be efficiently achieved. Another suggestion is to consider the completion process broken down into a number of key stages, from cube drilling strategies, all the way to flowback and cleanup (and everything in between).

With this stepwise breakdown, a useful approach may be to create a number of simple one-pagers that summarize the current best practice, indicate the most key recent industry publications, and any associated efforts that may be currently underway (e.g., through test sites).

While it would be appropriate for the SPE HyFTS to lead the one-pager compilation effort, the author(s) would be drawn directly from the most appropriate industry-recognized contributors.

Furthermore, information on key papers might be efficiently solicited from OnePetro statistics, major conference committee feedback (HFTC, URTeC, etc.) and other suggested sources. Following a fixed format, it is hoped that a suite (10–20) of these one-pagers could be quickly put together by the fracturing community and provide the SPE membership and body of engineers with a highly useful means of absorbing the current status of unconventional completion engineering.

This is definitely a work in progress, but the HyFTS aims to push this initiative forward as efficiently as possible so that the hydraulic fracturing community may quickly benefit. We have all been working in very different ways over the past 18 months and we believe that new ways of ensuring that best practice is being applied as swiftly as possible are welcome.

Those wishing to contribute to this effort in any way can lodge their support and participate from within the HyFTS where all contributions are welcome (https://connect.spe.org/hydraulicfracturing/home).

Martin Rylance, SPE, is the discipline lead and distinguished adviser for fracturing and stimulation at THREE60 Energy Ltd. Previously he worked at BP and its joint ventures and partner companies for more than 35 years. Having lived in 12 countries and pumped in 42, Rylance has international experience in fracturing and stimulation services, well control, and multilateral drilling. He is a coauthor of several books, including Modern Fracturing: Enhancing Natural Gas Production, and is author of more than 200 industry technical papers, articles, and patents. Rylance has been an SPE Distinguished Lecturer in 2007–2008, 2013–2014, and 2018–2019. He is a Distinguished Member of SPE and received the SPE Completions Optimization and Technology Award for the SPE Gulf Coast Section in 2015, and the SPE International Award in 2021. Rylance is a member of the JPT Editorial Review Committee and a director of the SPE Hydraulic Fracturing Technical Section and serves on multiple SPE committees. Rylance holds a BS degree from the University of Salford and is a Chartered Engineer and a Fellow of the Institute of Mathematics.